1. Field of the Invention
The present invention relates to optical fibers and, more particularly, to optical fiber joints and a method of joining optical fibers a transmission loss and suppress bends of the optical fiber core wires.
2. Description of the Prior Art
As shown in FIGS. 1-3, in a conventional optical fiber joint optical fiber core wires 2 each have a a plastic layer 1a or 1b, with the joined fiber core wires 2 being inserted into a plastic tubing 3 to form a core wire joint, and with the plastic tubing 3 then being heated and pressed at or above a temperature of the melting point of the plastic tubing 3 by a mold which includes a top and bottom member 4a and 4b so as to mold the plastic tubing 3 together with the joined optical fibers. The mold is thereafter cooled and an optical fiber joint 5 is obtained.
In the above described conventional optical fiber joint, the same material or a material fusible with the plastic layer 1a or 1b such as, for example, nylon may be utilized as the plastic tubing 3, with the plastic tubing 3 being merely heated and pressed by the top and bottom molds 4a and 4b, so that the optical fiber joint 5 can relatively easily be formed.
However, in a disadvantage of the conventional optical fiber joints and methods of joining the same resides in the fact that, if nylon is used for the tubing 3, a bending of the optical fiber core 2 occurs due to differences between the coefficients of thermal expansion of an optical fiber joint 5 at the time of forming such joint and after a completion of the joining processes so that a transmission loss of the optical fiber increases, or in certain cases, there a generation of bends having a bending radius of 30 mm or less which remarkably increases transmission loss, since nylon has a coefficient of thermal expansion of about twenty times that of the optical fiber core wire 2, i.e., 100-130.times.10.sup.-6 /.degree.C. than larger that of the optical fiber core wire 2.